Electron-beam Analyses of Individual Particles: Applicationsto Atmospheric Chemistry

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This is a project to determine the chemical and morphological characteristics of individual particles from tropospheric aerosols of remote areas in the Artic, North Atlantic, and Equatorial Pacific. Such particles in the planetary boundary layer and mid-troposphere are important because of their impact on the solar radiation balance, climate stability, and the global dispersion of natural and pollutant material. Analyses will be performed with automated electron- beam instruments. Methods developed over the past decade allow one to study large numbers of particles and to determine particle types, concentrations, and size distributions. The resulting data will be used to address current issues in atmospheric aerosol research. To be investigated are: (a) generation, fractionation, and reactions of marine aerosol particles; (b) production of natural, non-sea-salt sulfate particles; and (c) sources, transport, and fates of other particle types, both natural and anthropogenic. Automated particle analysis will be performed using a scanning electron microscope and an electron microprobe. As a secondary task, the structure and composition of complex submicron particles will be investigated at high spatial resolutions using transmission electron microscopy, both by imaging and by chemical analysis. The proposed studies, taken together, will provide fine-scale data about the chemical compositions, morphologies, and internal structures of a wide variety of individual particles. These data, in turn, will provide important insights into aerosol particle origins, chemical reactions, dispersion, and ultimate fates. //